Alteration of the sensory input to the visual system during postnatal development can permanently affect its anatomical, physiological and biochemical organization. In particular, it has been shown that the fibers of the optic radiation serving the left and right eye, which in the monkey normally terminate in alternating 400 micron m-wide bands (ocular dominance columns) in the fourth layer of the striate cortex, are affected by the imbalance in visual input produced by neonatal monocular lid-suture. Such deprivation allows fibers serving the open eye to gain a disproportionately large amount of cortical territory at the expense of those serving the closed eye: this change in the relative widths of the columns for the two eyes can be demonstrated by a number anatomical techniques as well as by physiological recording. The objectives of this research proposal are to examine the mechanisms for this plasticity by 1) determining the relationship between the time course of normal development of the columnar system and the period of sensitivity to deprivation, 2) testing experimentally hypotheses which attempt to explain the observed changes in terms of simple neuronal interactions, and 3) seeking evidence for changes in the synthesis or transport of molecules which may be involved in controlling these changes. Methods will be chosen which will permit the findings to be related to the known anatomical organization of the visual system. The include autoradiographic tracking of neural pathways in normal and visually deprived cats and monkeys at the light- and electron-microscopic level, microelectrode recording with subsequent histological reconstruction of electrode tracks, and autoradiography of neuronal protein and RNA metabolism in deprivation.